Professor develops water-saving AD process

By Lisa Gibson

Posted September 8, 2010 at 9:40 a.m. CST

A Colorado State University professor is developing an anaerobic digester that uses less water than conventional systems, making it ideal and economically feasible for use at feedlots and dairies in the western states.

Sybil Sharvelle, assistant professor of engineering, said her process is separated into stages, beginning with water trickling over the solids and converting the organic material into liquid organic acids. Then the acids are converted to methane in a separate high-rate digestion reactor. Sharvelle has experimented mainly with animal waste, but said the process is appropriate for any waste with solids content of more than 40 percent. "Aside from manure, we are also testing the reactor for conversion of the organic fraction of municipal solid waste to methane," she said. The amount of water saved varies depending on the quality of the feedstock, she added.

"This technology is very beneficial in the arid West where water is a precious resource and also has a high dollar value," Sharvelle said. "Agricultural producers in the West work hard to conserve water because they are often limited by water rights or have a financial benefit to do so." The water required for conventional AD technology generally renders it economically unfeasible, she added. "The lower water requirement for the system we are developing will enable agricultural producers in arid climates to generate revenue through installation of the technology."

Sharvelle and graduate student Luke Loetscher are collaborating with Fort Collins, Colo.-based Stewart Environmental Consultants Inc. and the university's Agricultural Experiment Stations to evaluate the feasibility of anaerobic digestion at Colorado feeding operations, according to the university. The system is currently operating on a laboratory scale, but construction of a pilot plant is underway at a Colorado feedlot. The pilot will operate over the next year, followed by construction of large operations in the second year and full commercialization in three years, according to Sharvelle.

Stewart Energy, a wholly owned subsidiary of Stewart Environmental Consultants Inc., is working to commercialize the process and has an exclusive option to license it from the Colorado State University Research Foundation.